Recently, ion generation apparatuses generating both positive ions and negative ions have been put to practical use. FIG. 13 is a perspective view showing a main portion of a conventional ion generation apparatus. In FIG. 13, the ion generation apparatus includes a substrate 51, an induction electrode 52 mounted on a surface of substrate 51, and two needle electrodes 58 and 59.
Induction electrode 52 is formed of one metal plate. Two through holes 54 and 55 are formed in a flat plate portion 53 of induction electrode 52, and a plurality of support portions 56 are formed at a circumferential portion of flat plate portion 53. A substrate insertion portion 57 having a width smaller than that of support portion 56 is formed at a lower end of each of support portions 56 at both ends of flat plate portion 53, and each substrate insertion portion 57 is inserted into a through hole in substrate 51 and soldered. Each of two needle electrodes 58 and 59 is inserted into a through hole in substrate 51 and soldered. Tip ends of needle electrodes 58 and 59 protrude from the surface of substrate 51, and are placed at the centers of through holes 54 and 55, respectively.
When positive high-voltage pulses and negative high-voltage pulses are applied between needle electrodes 58, 59 and induction electrode 52, respectively, corona discharge occurs at tip end portions of needle electrodes 58 and 59, and positive ions and negative ions are generated at the tip end portions of needle electrodes 58 and 59, respectively. The generated positive ions and negative ions are delivered into a room by an air blower, and surround and decompose molds or viruses floating in the air (see for example Japanese Patent Laying-Open No. 2007-305321 (Patent Document 1)).